precision oscillator overview - frequency...

Precision Precision Oscillator Oscillator Overview Overview

Hugo FruehaufApril [email protected]

Frequency Electronics Inc.Frequency Electronics Inc.

2Frequency Electronics Inc.Frequency Electronics Inc.

Discussion OutlineDiscussion Outline

• Quartz Crystal Oscillators• Atomic Oscillators • Atomic Oscillator Size History & Future• Performance Characteristics


Main Categories of Precision Quartz OscillatorsMain Categories of Precision Quartz Oscillators

Temperature Sensor

Compensation Network

XO

Temperature Compensated (TCXO)Temperature Compensated (TCXO)

Oven Control

Oven

XO

Temperature Sensor

Oven Controlled (OCXO)Oven Controlled (OCXO)

-45°c

-1 x 10-7

+1 x 10-7

+100°c

f

f∆

-45°c

-1 x 10-9

+1 x 10-9

+100°c

f

f∆

Ovens

XO

Temperature Sensors

Double Oven Controlled (DOCXO)Double Oven Controlled (DOCXO)

-45°c

-1 x 10-10

+1 x 10-10

+100°c

f

f∆

+25°c

Oven Controls

Quartz Crystal Oscillators have no wear out mechanism. If manufactured properly, should

last 25 years or more


X

Y

Z

Precision Crystal Oscillators from raw materialsPrecision Crystal Oscillators from raw materials

Piezoelectric Piezoelectric properties of quartzproperties of quartz

ResonatorResonator

Crystal OscillatorCrystal Oscillator

• Dynamic Cleaning• Crystal Cutting i.e.

SC, AT, FC, etc• Rounding• Polishing• Plating• Mounting• Tuning• Sealing• Testing

Typically 0.75” x 1.5” x 1.5”

Qz Disc


Typical Resonator Package ExamplesTypical Resonator Package Examples


The piezoelectric effect provides a coupling between the mechanical properties of a piezoelectric crystal and an electrical circuit.

Un-deformed lattice

X

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

++

__

_

_ _

_ _

_

_

_

_

_ _

_

_

_

_

_

_

_

Strained lattice

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

++

__

_

_ _

_ _

_

_

___

_ _

_

_

_

_

_

_

_

X• •- +

YY

_ _

Courtesy, John Vig (Ft. Monmouth NJ)

The Piezoelectric EffectThe Piezoelectric Effect


Flexure Mode Extensional Mode Face Shear Mode

Thickness Shear Mode

Fundamental ModeThickness Shear

Third OvertoneThickness Shear


Modes of Piezoelectric MotionModes of Piezoelectric Motion


x xl

y

φ

z

θ

θ

The AT, FC, IT, SC, BT, and SBTC-cuts are some of the cuts on the locus of zero temp. coefficient cuts.

90o

60o

30o

0

-30o

-60o

-90o0o 10o 20o 30o

AT FC IT

SC

SBTCBT

θ

φSingly

Rotated

Cut

DoublyRotatedCut


Zero Temperature Coefficient Quartz CutsZero Temperature Coefficient Quartz Cuts


TURNOVERPOINT

OVEN SET POINTTURNOVER

POINT

OVENOFFSET

2∆ To

OVEN CYCLING RANGE Typical f vs. T characteristicfor AT and SC-cut resonators

Freq

uenc

y

TemperatureCourtesy, John Vig (Ft. Monmouth NJ)

Oven Effect on Temperature CoefficientOven Effect on Temperature Coefficient


Mass transfer due to contaminationMass transfer due to contaminationSince f ∝ 1/t, ∆f/f = -∆t/t; e.g., f5MHz ≈ 106 molecular layers,therefore, 1 quartz-equivalent monolayer ⇒ ∆f/f ≈ 1 ppm

Stress reliefStress relief in the resonator's: mounting and bonding structure,electrodes, and in the quartz (?)

Other effectsOther effectsQuartz outgassingDiffusion effectsChemical reaction effectsPressure changes in resonator enclosure (leaks and outgassing)Oscillator circuit aging (load reactance and drive level changes)Electric field changes (doubly rotated crystals only)Oven-control circuitry aging

Aging MechanismsAging Mechanisms


TemperatureTemperatureControl temperature deltas with ovens

Frequency AgingFrequency AgingControl aging with superior manufacturing technology

Dynamic Environments (vibration, shock, acceleration)Dynamic Environments (vibration, shock, acceleration)Control sensitivity with:

- Superior manufacturing technology- Shock mounts- Electronic g-compensation technology

Summary Summary -- Most Significant EffectsMost Significant Effects


V i

b r a

t i o

n g

2 / H

z

300

0.2

0.3

0.4

0.5

10 100 1000

Frequency (Hz)

20 30 40 50 70

Loiter Aircraft

Helicopter

0

0.1 0.08g2/Hz0.04g2/Hz

200

Typical Loiter Aircraft and Helicopter Random Vibration Typical Loiter Aircraft and Helicopter Random Vibration

5g2/Hz


gg--Compensation TechnologyCompensation Technology

Z

X

Y Quartz Crystal Resonator base

Г = (x2 + y2 + z2)½Quartz Disk

The actual product

encloses the disk with a cap

Sensing devices mounted in each axis

Vibration applied to the Oscillator

Quartz Resonator responds

Sensing devices respond

Electronic Compensation

Oscillator Output[6]

[2]

[5]

[4]

[3]

[1]

[7]


–Acceleration sensitivities better than 2E-12/g

–Improvements of greater than 30dB –Optimized compensation from DC to 200 Hz

–Broadband compensation from DC to 2 KHz is possible

–Economies in manufacturability–Small package < 5in3

Uncompensated

Compensated

Uncompensated

Compensated

gg--Compensation & Shock Mount ApproachCompensation & Shock Mount Approach



• Quartz Crystal Oscillators

• Atomic Oscillators• Atomic Oscillator Size History & Future• Performance Characteristics


StandStand--alone Precision Oscillator alone Precision Oscillator TechnologiesTechnologies

Precision Quartz Crystal

Oscillators

Qz Osc.

Principle Oscillator in

use today

Rb Vapor Phy Pkg

Qz Osc.

Rubidium Vapor Atomic OscillatorRubidium Vapor Atomic Oscillator

Out• Qz oscillator

frequency-locked to Hyperfine Rb frequency of ~6.8 GHz

Cs Beam Phy Pkg

Qz Osc.

Cesium Beam Atomic StandardCesium Beam Atomic Standard

Out• Qz oscillator

frequency-locked to Hyperfine Cs frequency of ~9.2 GHz

Hydrogen Maser Atomic OscillatorHydrogen Maser Atomic Oscillator

Hm Fountain Phy Pkg

Qz Osc. Out

• Qz oscillator frequency-locked to Hyperfine Hm frequency of ~1.4 GHz (Passive Hm) orPhase-locked to ~1.4 GHz (Active Hm)

Atomic Oscillators

Quartz Quartz Crystal Crystal

OscillatorOscillator


Atomic Energy LevelsAtomic Energy Levels

Electron Energy Levels - Electrostatic interaction between Proton and Electron (+ and - charges)

Fine Structure - Interaction between electron spin dipole moment and the magnetic field due to the electron’s orbital motion. ~1/50 of the first energy level.

Collapsing the orbit releases energy

Expanding orbit requires energy

(Energy out or in is generally in the infrared-visible-UV frequencies)

(Energy out or in is generally in the microwave frequency area)

Hyperfine Structure - Magnetic dipole interaction between the electron spin dipole moment with the nucleus. ~1/1000 of fine structure interaction.

(Energy out or in is generally in the microwave frequencies and below)

f ≈ 1.4 GHz for Hydrogenf ≈ 6.8 GHz for Rubidiumf ≈ 9.2 GHz for Cesium

Zeeman Effect - Magnetic interaction between external magnetic field and electron and proton spin dipoles.

(Energy out or in is generally in the audio frequency area and above)

N

SN

S

(Courtesy: Ed Mattison, Smithsonian from his tutorial 12-92 (a H. Fruehauf modification of his chart)


Servo (8)

Synth(8a)

(5)

Heaters (2)

Lamp (4)

(could also be a Laser Diode)

Rubidium (1)

(could also be a Cesium Source)

Glass Cells (3)

(6)

Output

Qz Osc (9)

Atomic Vapor OscillatorAtomic Vapor Oscillator

~6.8 GHz

10 MHz

DC+Mod Freq

(1) Active Element of Choice(2) Controlled Environment(3) Element Container(4) Atomic Pump(5) Resonator(6) Irradiation Source(7) State Detector(s)(8) Control Electronics(9) Frequency Source

Photo Cell (7)

Atomic Vapor Oscillators have no wear out mechanism. If manufactured properly, should last 25 years or more

85Rb87Rb


Optical Pumping ProcessOptical Pumping ProcessDip Due to Rb

Resonance

Phot

o C

urre

nt

Microwave Frequencyfc

ttfm fm

fc<fRb fc>fRb

Mod

ulat

ed

Phot

o C

urre

nt

Out

put

t

fc=fRb

2fm

fmfmfm

ttt Freq

uenc

y M

odul

atio

n

fc<fRb fc=fRb fc>fRb

f

Resonance Cell87Rb 85Rb

Filter Cell

Photo Detector

Cavity (6.834, 682, 613 GHz)

87Rb Lamp

6.8 GHz from Osc.

C

BA

6.8 GHz Separation

Spectral Line

Filtered

Spectral Line

ExcitedN

S

N

S

(20 to 50 ns)

(~0.15 ns)


Dip Due to Rb ResonancePh

oto

Cur

rent

Microwave Frequencyfc

ttfm fm

fc<fRb fc>fRb

Mod

ulat

ed P

hoto

C

urre

nt O

utpu

t

t

fc=fRb 2fm

fm

ttt Freq

uenc

y M

odul

atio

n

fc<fRb fc=fRb fc>fRb

f

Modulation SchemeModulation Scheme

~500 Hz


Rubidium Vapor Atomic OscillatorRubidium Vapor Atomic Oscillator

Physics PackageSize: ~1.5” x ~3” x ~3”


Output

State Selection Magnets (7)

(2)

Cesium Source (1)

(5) (6)Beam Tube (3)

Cesium Beam Atomic Frequency StandardCesium Beam Atomic Frequency Standard

Cesium Oven (4)

(1) Active Element of Choice(2) Controlled Environment(3) Element Container(4) Atomic Pump(5) Resonator(6) Irradiation Source(7) State Detector(s)(8) Control Electronics(9) Frequency Source(10) Ion Pump and Getters

Hot Wire Ionizer (7)

5 MHz

~9.2 GHz

DC+Mod Freq

Qz Osc (9)

Servo (8)

Synth(8a)

Cesium Oscillators have a wear out mechanism, mainly due to the

detector getting noisy from un-gettered ions. It begins to show up

in 7 to 10 years

(10)


(2)

(5)

(6)

H

H2

Output

(2)

Bulb (3)

Hydrogen Source (1)Qz Osc

(9)

Servo (8)

Synth(8a)

(1) Active Element of Choice(2) Controlled Environment(3) Element Container(4) Atomic Pump(5) Resonator(6) Irradiation Source(7) State Detector(s)(8) Control Electronics(9) Frequency Source(10) Ion Pump and Getters

H2 Disassociator (4)

State Selection

Magnets (7)

Receiving Antenna (7)

~1.4 GHz~1.4 GHz

Passive Hydrogen Maser Atomic OscillatorPassive Hydrogen Maser Atomic Oscillator

Passive H-Maser Oscillators have a wear out mechanism, mainly

from Hydrogen depletion and Ion Pump failures, which begin to

show up in 5 to 7 years

(10)


(2)(5) & (9)

(6)

H

H2

Output

(2)

Bulb (3)

Hydrogen Source (1)Qz Osc

(8)

RCVR & PLL (8a) (1) Active Element of Choice

(2) Controlled Environment(3) Element Container(4) Atomic Pump(5) Resonator(6) Irradiation Source(7) State Detector(s)(8) Control Electronics(9) Frequency Source(10) Ion Pumps and Getters

H2 Disassociator (4)

State Selection

Magnets (7)

Receiving Antenna (7)

~1.4 GHz

Active Hydrogen Maser Atomic OscillatorActive Hydrogen Maser Atomic Oscillator

(6) No Irradiation Source; the Cavity Oscillates and thus is the Frequency Source, not the Qz Oscillator as in previous configurations

(10)

Active H-Maser Oscillators have a wear out mechanism, mainly from Hydrogen depletion and Ion Pump failures, which begin to show up in

3 to 5 years



• Quartz Crystal Oscillators• Atomic Oscillators

• Atomic Oscillator Size History & Future• Performance Characteristics


(1 in3

= 16.4 cm3)

1960 1970 1980 1990 2000 2010

Vol

ume

(siz

e) in

Cub

ic In

ches

10-1

100

101

102

103

104

105Vapor Std'sVapor Std Best GuessBeam StdBeam Std. Best Guess

~2400 in3 (HP, TRACOR, GENRAD)

~64 in3 (Efratom)

~5500 in3 (Lab)

~350 in3 (FTS)

~ 180 in3

47 in3 (Efratom)

24 in3 (Efratom, EG&G)

~13 in3(FEI, TNT)

~1 in3 ?

~1.0 cm3

(my guess, HF)

(DARPA Man-PacSpec, Low Pwr)0.6

0.3

0.18

Cesium Beam

Rb Vapor

60 in3

998583 93 02 06

Volume History of Rubidium and Cesium Osc.Volume History of Rubidium and Cesium Osc.

~7.35 in3 (Symmetricom)

6.03.0

1.8

~6.4 in3 (AccuBeat)

12 16



• Quartz Crystal Oscillators• Atomic Oscillators • Atomic Oscillator Size History & Future

• Performance Characteristics


Precise butnot accurate

Not accurate andnot precise

Accurate butnot precise

Accurate andprecise

Time TimeTimeTime

Stable butnot accurate

Not stable andnot accurate

Accurate butnot stable

Stable andaccurate

0

f fff

Accuracy, Precision, and StabilityAccuracy, Precision, and Stability

30Frequency Electronics Inc.Frequency Electronics Inc.Frequency (Hz)

dBc/

Hz

180

160

140

120

100

80

60

70

90

110

130

150

170

1KHz 10KHz 100KHz1Hz 10 Hz 100 Hz10-1

FEI State of Art

HP 10811 Qz

CMAC CFPO-LN

Qz Osc BestQz Osc Best--inin--Class Frequency Domain Noise Class Frequency Domain Noise (Phase Noise for a 10 MHz Carrier)(Phase Noise for a 10 MHz Carrier)

FEI-Zyfer 10 MHz- LN Module (- 4036)


FEI 6.3 MHz LN Osc. Test Plot, 03-09-2006

FEI State of Art Equivalent for 10 MHz

Measurement problem; should be at -165 floor

HP 10811 Qz



10-14

10-13

10-12

10-11

10-10

10-9

10-8

100 101 102 103 104

Averaging Time, T(Sec.)

HP 10811 Qz

1 Day10 Hrs.1 Hr

Qz Osc BestQz Osc Best--inin--Class Time Domain Noise Class Time Domain Noise (Short(Short--term Stability for 10 MHz)term Stability for 10 MHz)

10-3 10-2 10-1 105

Alla

n Va

rianc

e½, σ

y(τ)

FEI State of Art

FEI-Zyfer 10 MHz- LN Module (- 4036)


Comparison of Qz, Rb, GPS, Cs, and MaserComparison of Qz, Rb, GPS, Cs, and MaserTime Domain NoiseTime Domain Noise

Sym 5071A Option 001 Cs

10-16

10-15

10-14

10-13

10-12

10-11

10-10

1 10 102 103 104 105 106

Averaging Time, T(Sec.)

Sym 5061A, Cs

Sym 5071A, Cs GPS-Disciplined Qz/Rb

Kvarz Active Maser

Kvarz Passive Maser

1 Mo.1 Week1 Day

10 Hrs.1 Hr

()

() τ y21σ ,

Var

ianc

eA

llan

High Performance Rb

VREMYA (FEI) VCH-1006 Passive Maser

Good Qz Osc


10-16

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

1 10 100 1000 104 105 106 107 108

Short & Long Term Stability

Approx. Time Error at One Day (Lab Conditions)

1-Day 1-YearAveraging Time in Seconds Elapsed Time

~250 ms

~10 ms

~100 psActive - Hm

Passive - HmActive - HM

Passive - HM

Space Qz & Super OCXO

~300 µs

~90 µs

~30 µs

~10 µs

~1 µs

~86 ns

~25 ns

~3 ns

~1 ns

Hi-Perf. Cs

Hi-Perf. Space Rb

GPS/Rb (Cs Subst) & STD. Cs

Hi-Perf. Rb + Low Cost Space Rb

Low Cost RbSpace QzSuper OCXOOCXO

MCXO

TCXO

TCXO

Range

MCXO

OCXOLow Cost Rb

STD. CsGPS/Rb (Cs Substitute)

STD. Cs

(Alla

n Va

rianc

e) ½

[σγ(τ)

]

Hi-Perf. RbHi-Perf. Cs & Space Rb

Stability & Accuracy of Precision Oscillators Stability & Accuracy of Precision Oscillators Accuracy


500 MHz Osc Output; Best500 MHz Osc Output; Best--inin--Class Class Frequency Domain Noise Frequency Domain Noise

(Qz and SAW combo)(Qz and SAW combo)



Typical Specs for Precision Quartz OscillatorsTypical Specs for Precision Quartz OscillatorsBasic Parameters TCXO

(Temp. Comp. XO)OCXO (0.5” High)(Oven Control XO)

OCXO (0.75” High)(Oven Control XO)

DOCXO(Double Oven XO)

For Reference OnlyRubidium Osc.

Output 10 MHz, Sine0.5Vrms, 50 Ω

10 MHz, Sine0.5 Vrms, 50 Ω


10 MHz, Sine0.5 Vrms, 50Ω


Short Term Stab. 1s10s

100s

1 E-95 E-105 E-10

1E-111E-111E-10

5E-121E-111E-11

5E-121E-111E-11

3E-117E-123E-12

Phase Noise, 1Hz100Hz

1000Hz

- 55 dBc/Hz-115 dBc/Hz-130 dBc/Hz




-75 dBc/Hz-125 dBc/Hz-145 dBc/Hz

Aging/Day/Month/Year ---5E-7/yr

5E-10/day2E-7/yr

2E-10/day2E-8/yr

2E-10/day2E-8/yr

5E-11/day5E-10/yr

Temp RangeFrequency Stability

0° to 75°C5E-7

0° to 75°C2E-8*

0° to 75°C2E-9*

0° to 70°C2E-10

0° to 60°C3E-10

Power ConsumptionWarm-up Time

50 miliwatts50 milisec

2 watts10 min, 1E-8

2.5 watts10 min, 1E-8

3.5 watts10 min, 1E-8

8 watts4 min, ~1E-9

Magnetic Field SensitivityInput Volts RangeSupply Volts Sensitivity

---5 Vdc± 0.25%

1E-8 for +/-10%

---12 Vdc± 10%

---12 Vdc± 10%

---12 Vdc± 10%

2E-11/Gauss15 to 28 Vdc

SizeVolumeWeight

1.0” x 0.7” x 0.22” H0.154 in 3

< 0.1 lbs

1.5” x 1.5” x 0.5” H1.125 in3

< 0.15 lbs

2.0” x 2.0” x 0.75” H3 in3

< 0.22 lbs

2.0” x 2.0” x 1.0” H4 in 3

< 0.3 lbs

3.0” x 3.0” x 1.4” H13 in3

0.75 lbs

* With GPS learning algorithm, X20 improvement

1E-9 for +/-10% 1E-9 for +/-10% 1E-9 for +/-10% 2E-11 for +/-10%

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